Vacuum carburizing heat treatment process

What is the process of vacuum carburizing heat treatment? The following vacuum furnace factory is introduced.
1. Cleaning of parts. Parts surface is often accompanied by grease, rust and other contaminants, such as the existence of oils and fats, in the heart of the heating process will evaporate and carbonization, and thus contamination inside the furnace, block graphite, graphite felt parts such as fiber gap, change their performance, reduce its service life. At the same time, because grease of carbide and adhere to the surface of parts, a slow to carburizing heat treatment process, to extend the time of carburizing heat treatment, grain coarsening, permeability layers is not uniform, and reduces the mechanical properties of the parts, is bound to affect the heat treatment process and heat treatment quality, therefore, before the vacuum carburizing, should get rid of grease and other contaminants on the surface of the parts. For the cleaning of parts, it can be used for organic solvents, such as gasoline, which can be used for cleaning, and also can be used for special cleaning agent.
2. Placement of parts. For small parts, not pile up, can be small parts in stainless steel pressure interval to put online, not put, laying is a single layer, at the same time, with a stainless steel frame between the layers of network, it with no zinc wire and material box bound
3. Vacuum and start heating. To push the parts into the furnace, close the door of the furnace and start vacuuming. When the pressure in the furnace reaches 1.3x102pa, the power will be connected, heating furnace body and workpiece.

4. Heating and soaking. Due to the high vacuum degree of the furnace, heat transfer mainly depends on thermal radiation. Therefore, the heating speed is slower, which usually requires 1h (depending on the size of the workpiece) to reach the vacuum carburizing temperature.

Because the position of the workpiece is different and the heating speed is different, the workpiece facing the electric heater first absorbs heat and heats up quickly. The workpiece of the back to electric heater heats up slowly, so the heating temperature of the workpiece is not uniform. Therefore, after the temperature in the furnace reaches the carburizing temperature, it is necessary to have a mean heat phase. The purpose is to homogenize the temperature of the carburizing heat treatment workpiece and ensure the uniform carburizing layer. Further purify the surface of the workpiece, remove the surface oxidation film, remove the oil and activate the surface of the workpiece, so as to facilitate carburizing heat treatment.
5. Carburizing and diffusion. After the spare parts are evenly heated, the gas is permeated into the furnace, and the air pressure immediately picks up. Since the surface of the workpiece is clean, the carbon atom can absorb carbon atoms very well. The surface carbon concentration can reach a high level in a short time. After the scheduled time, it can stop ventilation and carry out the carbon diffusion.
6. Heat treatment after carburizing. Permeability layer is achieved after a power outage, ventilation with high purity, low dew point of nitrogen, in order to increase convection, speed up the cooling, the workpiece temperature drop, then exhaust, in order to refine the grain, but subsequent air cooled (below phase transition temperature) to heat, quenching process. In order to reduce the distortion, it can be precooled and chilled after carburizing.